is_partial problem with indexer

[tazarov]

When loading the index the indexer reports that functions are partial even when they are not. The issue is when parsing 'False' as boolean the bool() reports True.

We'll add the following utility method to deal with this bug:

def to_bool(value):
    """
       Converts 'something' to boolean. Raises exception for invalid formats
           Possible True  values: 1, True, "1", "TRue", "yes", "y", "t"
           Possible False values: 0, False, None, [], {}, "", "0", "faLse", "no", "n", "f", 0.0, ...
    """
    if str(value).lower() in ("yes", "y", "true", "t", "1"): return True
    if str(value).lower() in ("no", "n", "false", "f", "0", "0.0", "", "none", "[]", "{}"): return False
    raise ValueError('Invalid value for boolean conversion: ' + str(value))